The present invention relates to the treatment of steel work gases such as blast-furnace gas produced in metal treatment plants.
Currently, steel work gases (blast-furnace gases, coke-oven gases and converter gases) are burnt in conventional boilers, using atmospheric air as oxidizer. This arrangement does not allow significant thermal and/or electrical powers to be achieved. More recently, it has been proposed to burn steel work gases in gas turbines, thereby requiring expensive pretreatments (dust removal, compression to pressures up to 30 bar) of these gases and consequently require the compressors and combustion chambers of the turbines to be adapted.
The object of the present invention is to provide a novel process for the treatment of steel work gases, allowing them to be treated and utilized in an optimum fashion by burning them in a combustion section of a gas turbine and, downstream, in a recovery boiler, thus combining the production of electricity by the turbine with the efficient production of thermal energy in the recovery boiler.
To do this, according to one feature of the invention, the process for the treatment of steel work gases is characterized in that it comprises the steps of sending the steel work gas into at least one combustion section between the gas outlet of a gas turbine and the gas inlet of a recovery boiler and of burning the steel work gas in the said combustion section in order to produce steam in the recovery boiler.
Moreover, such a process offers great operating flexibility, being suitable for plants in which the flow rate and/or calorific value of the steel work gas vary/varies greatly.
This type of process also makes it possible to treat large volumes of steel work gas and, correspondingly, to achieve considerable installed powers, exceeding 200 MW.
According to other features of the invention:
the process includes the step of furthermore introducing a stream of fresh air, at least locally, into the combustion section in order to ensure combustion of the steel work gas;
the process includes the step of furthermore introducing a stream of combustible gas, at least locally, into the combustion section in order to guarantee combustion of the steel work gas, especially when its calorific value becomes very low.
Further features and advantages of the present invention will emerge from the following description of embodiments, the description being given by way of entirely non-limiting illustration, with reference to the appended drawing in which:
the single FIGURE schematically represents a combined plant for the implementation of a process according to the invention.